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Weather, time crunch equal more drift

Doreen Muzzi | Jun 11, 2003

A resulting memo from the Mississippi Bureau of Plant Industry warns pesticide applicators of the consequences of improper pesticide application, which can range from a letter of warning to a fine of up to $5,000 and/or commercial applicator license suspension.

“Farmers and commercial pesticide applicators should be aware at all times of wind conditions and should always follow product label directions. Application during unfavorable weather conditions is a violation of pesticide laws, and is subject to regulatory action that may include monetary penalties and license suspension,” said Michael Tagert, director of the Bureau of Plant Industry in Starkville, Miss.

Much of the blame for the increased incidences of drift is being attributed to two factors producers cannot control – weather, and time.

Extremely wet conditions in much of the North Delta this spring meant that growers had a limited amount of time available for weed control treatments.

“Growers were faced with a five-day window to get both their second application of glyphosate made on four-leaf Roundup Ready cotton, and their first glyphosate application made on Roundup Ready soybeans,” says Chip Morgan, executive vice president of Delta Council in Stoneville. “To make matters worse weather conditions weren’t always ideal even during this short window of time.”

While the majority of drift complaints in past years can be blamed on the off-target movement of burndown herbicides, the claims this year are primarily the result of in-season glyphosate treatments on Roundup Ready crops drifting on to susceptible crops, including conventional cotton and rice varieties.

“Our investigations have shown that ground applications as well as aerial applications have been involved,” the Mississippi Department of Agriculture and Commerce’s Tagert says.

“There have been some drift complaints related to aerial applications, but the majority of the claims that have been turned in to the Department of Agriculture are from ground applications of glyphosate, both by private and commercial applicators,” says Bob Howard of Howard Flying Service in Clarksdale, Miss.

“As aerial applicators we get blamed for a lot of things that we are not guilty of, and we always have to fight that rap. For instance, I recently sprayed a field, flying parallel to an adjacent blacktop road. Although I had to turn my plane over some houses, the wind was blowing away from the houses, and my spray nozzles were turned off. But simply because I flew over the houses, I received complaints that I had killed their gardens.”

Howard, who serves as president of the Mississippi Aerial Applicators Association, blames much of this year’s drift problem on a combination of cool temperatures, windy conditions, excessive rainfall, and seedling disease injury.

“It’s been a lot of things happening at one time. The wind has been our biggest enemy this year, but the cool nights, the big rains, and seedling diseases have also been detrimental to crop growth,” he says. “I feel the weather conditions made the crops more susceptible to drift injury, because the cool weather and rain weakened plants somewhat, and it didn’t take much to finish them off.”

Howard also believes Monsanto’s Roundup formulation played a part in the increased reports of drift injury. “I don’t know why, but this new Monsanto Roundup WeatherMax has drifted on us a whole lot worse than we expected. They say they haven’t changed the formulation any, but we’ve never had this much trouble before with the other glyphosate products from Monsanto,” he says.

A Monsanto spokesman contends there is no truth to claims that Roundup WeatherMax is more susceptible to drift than other glyphosate compounds.

“The biggest determinant of drift has nothing to do with product formulation. It has to do with wind speed,” says David Hollinrake, Monsanto’s Roundup marketing manager for the South and Southeast.

“There are three determinants to particle drift. One is particle size, which is determined by the spray tip you use. The second is speed of application, and the faster you travel the higher the probability of generating an off-target application. The third, and most important, is wind speed,” he says.

“Our label restricting application to wind speeds of less than 10 miles per hour is consistent with labels we’ve had in the past and is consistent across the industry with glyphosate products.”

Noting that “wind speed is always going to be very hard to predict,” Hollinrake says “the benefit of Roundup WeatherMax is that it gets into the plant very quickly. That’s crucial when your opportunity to make an application has been narrowed significantly due to weather conditions.”

For further information about pesticide drift, or to file a drift complaint, contact the Mississippi Bureau of Plant Industry at (662) 325-3390.